It is well known in the art of vehicle design that the fuel consumption of a vehicle associated with its movement is directly related to certain aerodynamic characteristics of the vehicle, such as the aerodynamic drag of the vehicle expressed as the drag coefficient, Cd. As the aerodynamic drag experienced by a vehicle increases, the fuel costs also correspondingly increase due to the greater energy required to overcome the drag. For example, for a vehicle traveling 70 mph on a roadway, approximately 65% of the total fuel consumption of its engine is used to overcome aerodynamic drag. Thus, even a slight reduction in the aerodynamic drag coefficient of the vehicle can result in a significant improvement in fuel economy.
For wheeled vehicles having one or more wheel assemblies supporting a body portion, aerodynamic drag is attributable in part to airflow impinging directly on the wheel assembly. In particular, wheeled vehicles having a body portion with a relatively high ground clearance, such as trailers in tractor-trailer towing arrangements, have a much larger wheel assembly exposed to the impinging airflow. Thus the need for reducing the aerodynamic drag of wheeled vehicles, especially land-based vehicles traveling at, for example, highway speeds, are compelling and widely recognized. It would therefore be advantageous to provide a simple cost-effective aerodynamic drag reduction apparatus which reduces the aerodynamic drag caused by the wheel assembly of a wheeled-axle vehicle, such as a tractor-trailer, to thereby reduce the net aerodynamic drag.